Abrasive articles generally comprise abrasive particles (also known as “grains”) retained within a binder. During manufacture of various types of abrasive articles, the abrasive particles are deposited on a binder material precursor in an oriented manner (e.g., by electrostatic coating or by some mechanical placement technique). Typically, the most desirable orientation of the abrasive particles is substantially perpendicular to the surface of the backing.
In the case of nonwoven abrasive articles, the binder material precursor is coated on a lofty open nonwoven fiber web, the abrasive particles are adhered to the binder material precursor, and then the binder material precursor is cured sufficiently to retain the abrasive particles during use.
In the case of certain coated abrasive articles (e.g., sandpaper), the backing is a relatively dense planar substrate (e.g., vulcanized fiber or a woven or knit fabric, optionally treated to a saturant to increase durability). A make layer precursor (or make coat) containing a first binder material precursor is applied to the backing, and then the abrasive particles are partially embedded into the make layer precursor. Frequently, the abrasive particles are embedded in the make layer precursor with a degree of orientation; e.g., by electrostatic coating or by a mechanical placement technique. The make layer precursor is then at least partially cured in order to retain the abrasive particles when a size layer precursor (or size coat) containing a second binder material precursor is overlaid on the at least partially cured make layer precursor and abrasive particles. Next, the size layer precursor, and the make layer precursor if not sufficiently cured, at cured to form the coated abrasive article.
For both of the above types of abrasive articles it is generally desirable that the abrasive particles remain in their original orientation as embedded in the binder material precursor until it have been sufficiently cured to fix them in place. This is especially troublesome when the binder precursor material is too fluid so that the particles tip over by gravity, or if the binder precursor material is too hard such that the particle do not adhere to the binder precursor material and again tip over due to gravity.
Abrasive particle tipping after deposition is especially problematic with resole phenolic resin binder material precursors. It would be desirable to have resole-phenolic-resin-based binder material precursors that the original orientation of the applied abrasive particles until curing.